title: Human LINE-1 restriction by APOBEC3C is deaminase independent and mediated by an ORF1p interaction that affects LINE reverse transcriptase activity.
abstract: LINE-1 (L1) retrotransposons are mobile genetic elements whose extensive proliferation resulted in the generation of ≈ 34% of the human genome. They have been shown to be a cause of single-gene diseases. Moreover, L1-encoded endonuclease can elicit double-strand breaks that may lead to genomic instability. Mammalian cells adopted strategies restricting mobility and deleterious consequences of uncontrolled retrotransposition. The human APOBEC3 protein family of polynucleotide cytidine deaminases contributes to intracellular defense against retroelements. APOBEC3 members inhibit L1 retrotransposition by 35-99%. However, genomic L1 retrotransposition events that occurred in the presence of L1-restricting APOBEC3 proteins are devoid of detectable G-to-A hypermutations, suggesting one or multiple deaminase-independent L1 restricting mechanisms. We set out to uncover the mechanism of APOBEC3C (A3C)-mediated L1 inhibition and found that it is deaminase independent, requires an intact dimerization site and the RNA-binding pocket mutation R122A abolishes L1 restriction by A3C. Density gradient centrifugation of L1 ribonucleoprotein particles, subcellular co-localization of L1-ORF1p and A3C and co-immunoprecipitation experiments indicate that an RNA-dependent physical interaction between L1 ORF1p and A3C dimers is essential for L1 restriction. Furthermore, we demonstrate that the amount of L1 complementary DNA synthesized by L1 reverse transcriptase is reduced by ≈ 50% if overexpressed A3C is present.
authors.affiliation: Section PR2/Retroelements, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany, Department of Embryology, Carnegie Institution of Washington, 3520 San Martin Drive, Baltimore, MD 21218, USA, Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany, Clinic for Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany and Biostatistics Section, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany.
authors.forename: Axel V
authors.initials: AV
authors.lastname: Horn
authors.forename: Sabine
authors.initials: S
authors.lastname: Klawitter
authors.forename: Ulrike
authors.initials: U
authors.lastname: Held
authors.forename: André
authors.initials: A
authors.lastname: Berger
authors.forename: Ananda Ayyappan Jaguva
authors.initials: AA
authors.lastname: Vasudevan
authors.forename: Anja
authors.initials: A
authors.lastname: Bock
authors.forename: Henning
authors.initials: H
authors.lastname: Hofmann
authors.forename: Kay-Martin O
authors.initials: KM
authors.lastname: Hanschmann
authors.forename: Jan-Hendrik
authors.initials: JH
authors.lastname: Trösemeier
authors.forename: Egbert
authors.initials: E
authors.lastname: Flory
authors.forename: Robert A
authors.initials: RA
authors.lastname: Jabulowsky
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Han
authors.forename: Johannes
authors.initials: J
authors.lastname: Löwer
authors.forename: Roswitha
authors.initials: R
authors.lastname: Löwer
authors.forename: Carsten
authors.initials: C
authors.lastname: Münk
authors.forename: Gerald G
authors.initials: GG
authors.lastname: Schumann
mesh_terms: D002352:Carrier Proteins / Q000032:analysis; D003564:Cytidine Deaminase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000201:enzymology; D004265:DNA Helicases; D006367:HeLa Cells; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D009154:Mutation; D000075223:Poly-ADP-Ribose Binding Proteins; D055503:Protein Multimerization; D011506:Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D020365:RNA Helicases; D000067776:RNA Recognition Motif Proteins; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C531245:ORF1 protein, human; D000075223:Poly-ADP-Ribose Binding Proteins; D011506:Proteins; D000067776:RNA Recognition Motif Proteins; D012194:RNA-Directed DNA Polymerase; C121399:APOBEC3A protein, human; C495795:APOBEC3C protein, human; D003564:Cytidine Deaminase; D004265:DNA Helicases; C116070:G3BP1 protein, human; D020365:RNA Helicases